away. The three-star General followed him, with Ryan trailing behind.
Inside the van, where the temperature might have been merely at freezing, a chief warrant officer was rewinding a videotape.
'Where were the targets?' Jack asked. 'That wasn't in the briefing papers.'
'About forty-five south, thirty west,' the General replied. Major Gregory was perched in front of the TV screen.
'That's around the Falklands, isn't it? Why there?'
'Closer to South Georgia, actually,' the General replied. 'It's a nice, quiet, out-of-the-way sort of place, and the distance is about right.'
And the Soviets had no known intelligence-gathering assets within three thousand miles, Ryan knew. The Tea Clipper test had been timed precisely for a moment when all Soviet spy satellites were under the visible horizon. Finally, the shooting distance was exactly the same as the distance to the Soviet ballistic missile fields arrayed along the country's main east-west railway.
'Ready!' the warrant officer said.
The video picture wasn't all that great, taken from sea level, specifically the deck of the Observation Island, a range instrumentation ship returning from Trident missile tests in the Indian Ocean. Next to the first TV screen was another. This one showed the picture from the ship's 'Cobra Judy' missile-tracking radar. Both screens showed four objects spaced in a slightly uneven line. A timer box in the Iowa right-hand corner was changing numbers as though in an Alpine ski race, with three digits to the right of the decimal point. 'Hit!' One of the dots disappeared in a puff of green ligth.
'Miss!' Another one didn't.
'Miss!' Jack frowned. He'd half-expected to see the beam of light streaking through the sky, but that happened only movies. There wasn't enough dust in space to denote the energy's path.
'Hit!' A second dot vanished. 'Hit!' Only one was left.
'Miss.'
'Miss.' The last one didn't want to die, Ryan thought.
'Hit!' But it did. 'Total elapsed time, one point eight-zero-six seconds.'
'Fifty percent,' Major Gregory said quietly. 'And it corrected itself.' The young officer nodded slowly. He managed to keep from smiling, except around the eyes. 'It works.'
'How big were the targets?' Ryan asked.
'Three meters. Spherical balloons, of course.' Gregory was rapidly losing control. He looked like a kid whom Christmas had taken by surprise.
'Same diameter as an SS-18.'
'Something like that.' The General answered that one.
'Where's the other mirror?'
'Ten thousand kilometers up, currently over Ascension Island. Officially it's a weather satellite that never made its proper orbit.' The General smiled.
'I didn't know you could send it that far.'
Major Gregory actually giggled. 'Neither did we.'
'So you sent the beam from over there to the shuttle's mirror, from Discovery to this other one over the equator, and from there to the targets?'
'Correct,' the General said.
'Your targeting system is on the other satellite, then?'
'Yes,' the General answered more grudgingly.
Jack did some numbers in his head. 'Okay, that means you can discriminate a three-meter target at? ten thousand kilometers. I didn't know we could do that. How do we?'
'You don't need to know,' the General replied coldly.
'You had four hits and four misses-eight shots in under two seconds, and the Major said the targeting system corrected for misses. Okay, if those had been SS-18s launched off of South Georgia, would the shots have killed them?'
'Probably not,' Gregory admitted. 'The laser assembly only puts out five megajoules. Do you know what a joule is?'
'I checked my college phyzzies book before I flew down. A joule is one newton-meter per second, or zero- point-seven foot-pounds of energy, plus change, right? Okay, a megajoule is a million of them? seven hundred thousand foot-pounds. In terms I can understand-'
'A megajoule is the rough equivalent of a stick of dynamite. So we just delivered five sticks. The actual energy transferred is like a kilogram of explosives, but the physical effects are not exactly comparable.'
'What you're telling me is that the laser beam doesn't actually burn through the target-it's more of a shock effect.' Ryan was stretching his technical knowledge to the limit.
'We call it an 'impact kill,' ' the General answered. 'But, yeah, that's about it. All the energy arrives in a few millionths of a second, a lot faster than any bullet does.'
'So all that stuff I've heard about how polishing the missile body, or rotating it, will prevent a burn- through-'
Major Gregory giggled again. 'Yeah, I like that one. A ballet dancer can pirouette in front of a shotgun and it'll do her about as much good. What happens is that the energy has to go somewhere, and that can only be into the missile body. The missile body is full of storable liquids-nearly all of their birds are liquid fueled, right? The hydrostatic effect alone will be to rupture the pressure tanks-ka-boom! no more missile.' The Major smiled as though describing a trick played on his high-school teacher.
'Okay, now, I want to know how it all works.'
'Look, Dr. Ryan-' the General started to say. Jack cut him off.
'General, I am cleared for Tea Clipper. You know that, so let's stop screwing around.'
Major Gregory got a nod from the General. 'Sir, we have five one-megajoule lasers-'
'Where?'
'You're standing right on top of one of them, sir. The other four are buried around this hilltop. The power rating is per pulse, of course. Each one puts out a pulse-chain of a million joules in a few microseconds-a few millionths of al second.'
'And they recharge in??'
'Point zero-four-six seconds. We can deliver twenty shots per second, in other words.'
'But you didn't shoot that fast.'
'We didn't have to, sir,' Gregory replied. 'The limiting factor at present is the targeting software. That's being worked on. The purpose of this test was to evaluate part of the software package. We know that these lasers work. We've had them here for the past three years. The laser beams are converged on a mirror about fifty meters that way'-he pointed-'and converted into a single beam.'
'They have to be-I mean, the beams all have to be exactly in tune, right?'
'Technically it's called a Phased-Array Laser. All the beams have to be perfectly in phase,' Gregory answered.
'How the hell do you do that?' Ryan paused. 'Don't bother, I probably wouldn't understand it anyway. Okay, we have the beam hitting the downside mirror?'
'The mirror is the special part. It's composed of thousands of segments, and every segment is controlled by a piezoelectric chip. That's called 'adaptive optics.' We send an interrogation beam to the mirror-this one was on the shuttle-and get a reading on atmospheric distortion. The way the atmosphere bends the beam is analyzed by computer. Then the mirror corrects for the distortion, and we fire the real shot. The mirror on the shuttle also has adaptive optics. It collects and focuses the beam, and sends it off to the 'Flying Cloud' satellite mirror. That mirror refocuses the beam on the targets. Zap!'
'That simple?' Ryan shook his head. It was simple enough that over the previous nineteen years, forty billion dollars had gone into basic research, in twenty separate fields, just to run this one test.
'We did have to iron out a few little details,' Gregory acknowledged. These little details would take another five or more years, and he neither knew nor cared how many additional billions. What mattered to him was that the goal was now actually in sight. Tea Clipper wasn't a blue-sky project anymore, not after this system test.
